Homogeneous catalyst formulations for methanol production

ABSTRACT

There is disclosed synthesis of CH3OH from carbon monoxide and hydrogen using an extremely active homogeneous catalyst for methanol synthesis directly from synthesis gas. The catalyst operates preferably between 100 DEG -150 DEG  C. and preferably at 100-150 psia synthesis gas to produce methanol. Use can be made of syngas mixtures which contain considerable quantities of other gases, such as nitrogen, methane or excess hydrogen. The catalyst is composed of two components: (a) a transition metal carbonyl complex and (b) an alkoxide component. In the simplest formulation, component (a) is a complex of nickel tetracarbonyl and component (b) is methoxide (CH3O13 ), both being dissolved in a methanol solvent system. The presence of a co-solvent such as p-dioxane, THF, polyalcohols, ethers, hydrocarbons, and crown ethers accelerates the methanol synthesis reaction.

The U.S. Government has rights in this invention pursuant to ContractNumber DE-AC02-76CH00016, between the U.S. Department of Energy andAssociated Universities Inc.

RELATED APPLICATIONS

This application is a continuation-in-part of co-pending applicationSer. No. 943,731 filed Dec. 19, 1986 and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to novel homogeneous catalyst formulations formethanol production. These new formulations have a number of features:liquid phase performance, low temperature, low pressure performance,high activity, and high selectivity, which permits gas conversions inone pass through greater than 90%, and under optimum conditions gasconversions of about 97%. Since this catalyst system is a liquid phasesystem, it permits the reaction between carbon monoxide and hydrogen toform methanol, which is an exothermic reaction, to proceed at fullyisothermal conditions. In contrast, the traditional pelleted, solidcatalysts used in methanol production create hot spots in the reactorwhich prevent the process from operating efficiently. Further, becausethe homogeneous catalyst is in solution, reaction heat removal can bedecoupled from kinetics. Thus, unlike existing processes, with theinstant process optimum performance, both chemically and thermally, canbe built into the production system separately, with the components ofthe production system designed to optimize heat removal and kinetics.

The homogeneous catalyst formulation of the present invention overcomesother disadvantages of conventional, solid-phase, methanol synthesiscatalysts. Typically, conventional processes require high temperatures(250° C.) and high pressure (765 psi) and are limited by low equilibriumconversion (60%). Using the catalysts of the present invention, methanolproduction can be conducted at low temperatures and pressure with a highequilibrium conversion.

Further, conventional type catalysts, such as pellet type catalysts,usually exhibit a gas conversion rate of about 16-30% per pass,necessitating the re-cycling of the feed gas in order to operate theproduction system at an economically acceptable efficiency. Thus,although partial oxidation of natural gas yields an ideal methanol feedgas, partial oxidation cannot be used to produce the feed gas forconventional catalyst systems because such systems require a feed gaswith very low levels of inert gases, especially nitrogen. Inerts such asnitrogen that build up in the recycle stream must be kept low forprocess efficiency. To produce feed gases with low levels of inerts, thepartial oxidation would have to be carried out using oxygen and thisapproach renders this method of feed gas preparation economicallyunfeasible. The instant catalyst system makes it possible to takeadvantage of partial oxidation production of the synthesis feed gasbecause the high conversion eliminates the need for a recycle stream andthereby permits use of air rather than oxygen, saving the large costsfor oxygen generation. A further improvement that results from the highefficiency of the process that permits one pass through operation isthat the atmospheric nitrogen that enters the system through the airpartial oxidation step leaves the reactor at reaction pressure and canbe expanded to provide energy, for example for air compression.

The present invention provides a homogeneous catalyst that permits theproduction of methanol from a synthesis gas feed gas containing inertgases, at low temperatures and pressures and at high gas conversionrates. This represents a significant improvement in reaction conditionsand process efficiency over the conventional methanol catalysts.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention covers a novel homogeneous catalyst which can beused for the synthesis of methanol from carbon monoxide and hydrogen.This homogeneous catalyst is easily prepared; it exhibits superioractivity when compared to conventional methanol catalysts, it permitsthe use of lower temperatures and pressures in the reactor, it permitsthe use of a feed gas that contains inert gases in addition to the COand H₂, and it produces high gas conversion rates.

The homogeneous catalyst of the present invention is comprised of twocomponents dissolved in methanol or a methanol and co-solvent mixture.The two components are a transition metal carbonyl complex and analkoxide. The transition metal is selected from the group consisting ofcopper, nickel, palladium, cobalt, ruthenium, iron, molybdenum andmixtures of these metals. The preferred transition metal is nickel.

This two component catalyst is in a solution of methanol, which isavailable from the methanol product in the reactor. A co-solvent mayalso be employed, preferably an organic oxygen containing co-solventthat is miscible with methanol. Suitable co-solvents include saturatedhydrocarbons, amine based solvents, ethers, esters, alkyl polyethers andhydroxyalkylpolyethers in which the carbon chain is interrupted by oneor more oxy groups, and alcohols. The preferred co-solvents aretetrahydrofuran, 2-methyltetrahydrofuran, iso-octane, toluene,p-dioxane, t-amyl alcohol, t-butyl alcohol, polyalcohols, glycolderivatives such as polyethylene glycol and triglyme, the dimethyl etherof resorcinol, dimethyl oxalate, and crown ethers.

Because the homogeneous catalyst of the present invention possesses suchhigh activity, the catalyzed production of methanol from carbon monoxideand hydrogen can be carried out under moderate conditions. The catalystoperates effectively at temperatures in the range of from 20° C. to 150°C., with temperatures in the range of 100°-150° C. being preferred.Likewise the pressure prevailing in the reactor can be as low as 50 psiand as high as 300 psi with the preferred pressure being in the range of100-150 psi.

The feed gas for the production of methanol using the present catalystis preferably synthesis gas produced by the air partial oxidation ofnatural gas. This feed gas may be diluted with inert gases such asnitrogen and methane. The catalyst can tolerate minor quantities ofhydrogen sulfide, carbon dioxide and water but it is preferred to use anapproximately anhydrous, carbon dioxide-free synthesis gas.

The homogeneous catalyst of the present invention is the product of thereaction between the two materials used to prepare the catalyst, thetransition metal material and the alkoxide material. The transitionmetal material is a material capable of generating the correspondingtransition metal carbonyl in a methanol solution. The transition metalmaterial may be the metal carbonyl or a carbonyl precursor. As usedherein, the term carbonyl precursor means a material which, whendissolved in methanol, forms the transition metal carbonyl in situ. Thetransition metal carbonyl or transition metal carbonyl precursor may beused in the preparation of the instant catalyst in its mononuclear formor in cluster form. With the preferred transition metal, nickel, anyform of nickel carbonyl, such as nickel tetracarbonyl, Ni(CO)₄, or anycarbonyl precursor capable of generating the carbonyl nickelate in themethanol solution can be used in the preparation of the homogeneouscatalyst. It is also possible to use a bi-metallic system in which amixture of two transition metal carbonyls, or carbonyl precursors, isused, for instance nickel carbonyl and molybdenum carbonyl. In anotheraspect of using a bi-metallic system, a transition metal carbonyl orcarbonyl precursor, for instance nickel tetracarbonyl, is used, togetherwith the alkoxide contributing material, such as potassium methoxide,and in addition a transition metal alkoxide is also used, such as coppermethoxide.

The transition metal carbonyl or carbonyl precursor material may also beintroduced into the methanol solution in which the homogeneous catalystis to be prepared in the form of any supported species which will form,for instance, the carbonyl nickelate, on its surface. In this way thehomogeneous catalyst will be carried on a support, like zeolite, so thatthe system could function as either a homogeneous or heterogeneouscatalyst.

The second material used in the preparation of the homogeneous catalystis the material that contributes the alkoxide component. Useful as thissecond reaction material is any metal, amine, or other material whichwill form or generate alkoxides in the presence of the methanol solventsystem. Possible alkoxide generators are group IA, IIA and IIB metalalkoxides, where the alkoxy group is preferably derived from alcoholscontaining 1-6 carbon atoms. Preferred are the aliphatic alcoholateswhere the cation is an alkali or alkaline earth metal or a mixturethereof. Most preferred are the aliphatic alcoholates of sodium,potassium, rubidium, cesium, barium and calcium; with potassiummethoxide most preferred. Examples of amines that will generate analkoxide in a methanol solution are 1,8-diazobicyclo[5.4.0]undec-7-eneand tetramethylammonium methoxide.

When the alkoxide contributing material is added to the reactor duringpreparation of the homogeneous catalyst, it is also possible to add amaterial that will inactivate the cation or non alkoxide ion throughphysico-chemical interactions in order to increase the concentration ofthe alkoxide ion in solution. Suitable complexation and/or coordinationmaterials or ligands for this purpose include crown ethers, crystandsand multidentates for alkali and alkaline earth cations. Preferredcomplexation and/or coordination ligands include 2,2-bipyridine,diethyleneglycoldimethyl ether or 15-Crown-5 with sodium,tetramethylethylenediamine or triethanolamine with lithium, anddibenzo-18-Crown-6 with potassium (see Chem. Rev., 79, 415, 1979).

In a further aspect of the process by which the homogeneous catalyst ofthe present invention is prepared, it is possible to employ solventadditives that accelerate the reaction of the metal and alkoxidecatalyst components. As an example, it is possible to add to themethanol solution nickel carbonyl activators such as sodium sulfide,thioacetamide, mercury ions, borate ions, for instance from boric acid,borate esters, and thioamides such as thiocarboxylic acid amides,thioazole, thioureas, mustard oils, thiocarbamic acid derivatives,thiuram disulfides, and rhodamic acid.

In the preferred homogeneous catalyst formulation, the transitionalmetal component is a complex of nickel tetracarbonyl and the alkoxidecomponent is the methoxide anion, MeO¹³, with the preferred associatedcation being either an alkali metal (Na, K) or a non-alkali metal suchas tetramethylammonium; these preferred cations increase the solubilityof the catalyst components dissolved in methanol solvents. Theproportions of the metal and alkoxide components in the catalystformulation will vary, depending upon whether methanol is used alone asthe solvent or whether a co-solvent is used. Basically, the amount ofmetal and alkoxide in one liter of methanol containing solvent systemvaries from about 0.01-2 moles of metal compound and 0.01-20 moles ofalkoxide. If methanol alone is the solvent, the preferred molar ratio is1/100 while if tetrahydrofuran is used as a co-solvent, the preferredmolar ratio is 1/0.5.

Batch methanol synthesis rates as high as 300 psi/min have been achievedwith the homogeneous catalysts of the present invention. The simplicityof this active catalyst lies in the fact that the product (methanol)serves as the solvent and the alkoxide component can be derived from theproduct making the system mechanistically simple and economicallyattractive. The product methanol can be removed from the reaction zonetogether with non-reacted CO and H₂ as a gas simultaneously with itsformation by the chemical reaction in the liquid phase. The catalyst isextremely selective for methanol synthesis. Conversions to methanol ofas high as 94% are consistently achieved. The rate at which carbonmonoxide and hydrogen react can be increased by carrying out thereaction in the presence of a co-solvent. Particularly recommended areTHF, 2 methyl-THF, p-dioxane, t-amyl alcohol, t-butyl alcohol, triglymeand the polyethylene glycols, known as PEG-200 and PEG-400. The aboveco-solvents are preferably applied in molar or almost molar proportionswith respect to methanol. If desired, however, also larger or smallerquantities may be chosen.

Since the reaction between CO and H₂ to form methanol catalyzed by thehomogeneous catalyst of the present invention occurs in a liquidreaction phase, the feed gas can be supplied to the catalyst forcontacting in any reactor that is designed for liquid phase/gas systemoperation. Likewise, the methanol production can be carried out in areactor system designed for batch, semi-continuous or continuousproduction.

It is preferred to carry out the production of methanol using theinstant catalyst using a reactor that is characterized by good mixtureof the gas/liquid phases. The methanol product is removed from thereactor by bubbling an excess of carbon monoxide and hydrogen, or aninert carrier gas such as nitrogen, through the reactor. By removingmethanol as a gas, the technical advantages to the production processassociated with the catalyst, its activity, lifetime, and handling areachieved. Alternatively, methanol can be removed in the liquid phase sothat dissolved catalyst is carried with product flow from the reactor.Products are flashed in a separation zone and recovered catalyst isrecirculated to the reactor.

The combination of low operating temperature needed by the instantcatalyst and its high catalytic activity at very short contact timesmakes it possible to achieve very high conversion rates of the feed gasin the methanol synthesis. Equilibrium conversion of syngas having 2mols of hydrogen per mol of carbon monoxide at 100° C. and 150 psi hasconsistently been calculated to be about 94%. Furthermore, the liquidnature of the catalyst systems makes it possible to decouple gas liquidcontacting for fast reaction from the removal of heat resulting from theexothermic reaction of CO and H₂ from the reactor. This decoupling canbe done, for example, by circulating the catalyst through an externalcooler or incorporating an inert low-boiling compound into the catalystsystem which can be condensed externally and recycled to the reactor.The combination of the process' high thermodynamic equilibria and theability to decouple kinetics and heat transfer overcomes reactor designlimitations imposed by current catalyst technology.

In one embodiment of the present invention, the homogeneous catalyst isprepared in situ in the reactor by adding the transition metal carbonylcontributing material and the alkoxide contributing material to asolution of methanol and desired co-solvents, activators, etc. Methanolproduction can proceed immediately upon catalyst preparation. In analternative approach, the homogeneous catalyst can be preparedseparately in advance and loaded into the reactor when needed.

In one embodiment for methanol synthesis using the liquid phase catalystof the present invention, feed synthesis gas enters the reactor whichoperates at 110° C. and 150 psi. Gas rises through the catalyst solutionand forms methanol releasing heat which is removed, for example, bycirculation of a coolant through coils in the reactor. Though thiscooling system does not completely decouple cooling from reactioninterface conditions, heat transfer to the coils is rapid and thereaction proceeds essentially isothermally at a favorable temperaturebecause of the vigorous agitation and turbulence of the liquid inducedby gas flow. As a result, conversion of 90% of the carbon monoxide canbe achieved. The tail gas is, therefore, very small in volume and thecooler, separator and recycle compressor for recycling unconverted gasare very small in comparison to the requirements of similar componentsused with conventional heterogeneous catalysis. The small volume of gasmay be insufficient to carry all the methanol overhead as vapor. In sucha case, it is necessary to extract liquid from the reaction. This liquidis blended with condensate from the separator and constitutes the crudemethanol which flows from the separation system. When liquid is removedfrom the reactor, the first distillation tower separates volatilecatalyst components and returns them to the reactor. The seconddistillation tower produces methanol product as distillate. If thisapproach is taken to the production of methanol, and a co-solvent is tobe used in the system, a co-solvent will be chosen that has a boilingpoint higher than methanol so that the methanol and co-solvent areseparated in the second distillation tower and the co-solvent isreturned as a liquid to the reactor.

The methanol process of the present invention is made possible by thediscovery of this low temperature liquid catalyst which can convertsynthesis gas almost completely to methanol in a single pass through themethanol synthesis reactor. This characteristic allows atmosphericnitrogen to be tolerated in the synthesis gas and still the volume ofgas fed to the reactor can be smaller than the gas volume needed incurrent synthesis reactors. Table 1 below sets forth a comparisonbetween the instant process and a conventional methanol catalysisprocess. Significant improvements are noted in both reaction conditionsand product yields.

                  TABLE 1                                                         ______________________________________                                                       Methanol                                                                      Production                                                                             Methanol                                                             Catalyzed By                                                                           Production                                                           Homogeneous                                                                            By Conventional                                                      Catalyst Catalysis*                                            ______________________________________                                        Reactor Temperature, °C.                                                                110        265                                               Reactor pressure, psia                                                                         150        750                                               Equilibrium CO conversion, %                                                                    94        61                                                Operating CO conversion, %                                                                      90        16                                                Volume of gas recycle,                                                                         0.11       5.25                                              mols CO/mol product                                                           Reactor feed,    1.11       6.25                                              mols CO/mol product                                                           Overhead gas cooling duty,                                                                     4,100      71,000                                            Btu/mol product                                                               Separator temperature                                                                          163        77                                                for 95% product recovery, °F.                                          ______________________________________                                         *Supp. E, Hydrocarbon Processing, March 1981, pp 71-75 and Hydrocarbon        Processing, July 1984, pp 34C-34J                                        

The following examples will further illustrate the invention but theinvention is not restricted to these examples. In the examples set forthbelow, the total pressure in the reactor varied from about 765 psia atthe start of each run to about 50-150 psia when the reaction wasterminated; this final pressure is equivalent to the desired operatingpressure of continuous reactor.

EXAMPLE 1

Sodium t-amyl alkoxide (40 mmol), prepared by reacting NaH (40 mmol)with a slight excess of t-amyl alcohol (52 mmol) in 30 mL THF, was addedto the reactor along with 70 mL THF to give 100 mL total THF. Thereactor was flushed with H₂. 10 mmol Ni(CO)₄ was added and the reactorwas pressurized with 300 psig syngas (2H₂ :1CO). On heating to 100° C.,the gas consumption rate was 3, 8, 7 psi/min, respectively, duringfirst, second, and third charge (300 psi each) respectively. 164 mmolmethanol was produced corresponding to 86% gas consumption.

EXAMPLE 2

This example shows the effect of alkali metal on rate. The alkoxidepreparation and reactor loading described in Example 1 was repeatedusing potassium hydride in place of sodium hydride. Thus, 40 mmolK-t-amyl alkoxide was prepared by reaction of KH (40 mmol) with 52 mmolt-amyl alcohol in 30 mL THF. The resulting solution was poured into thereactor and 70 mL additional THF was added. The reactor was sealed andpurged with H₂ and 10 mmol Ni(CO)₄ was added. 300 psi syngas (2H₂ :1CO)was added to the reactor and the reactor was heated to 100° C. Theaverage gas consumption rate was 32, 50, 22, 7.5 psi/min for charges 1(300 psi), 2 (300 psi), 3 (300 psi), 4 (750 psi), respectively. 0.35 molmethanol was produced.

EXAMPLE 3

This example illustrates the positive effect of increasing alkoxideconcentration on rate and shows that the process is truly catalytic inbase and nickel. K-t-amyl alkoxide was increased to 100 mmol from 40mmol and the procedure described in Example 2 was followed. The averagerate was 54, 275, 64 psi/min for charges 1 (300 psi) and 2, 3, 4, 5 (750psi each). 1 mol methanol corresponding to 94% gas conversion wasproduced. Methanol produced corresponds to at least 100 cycles in Ni and10 cycles in base, proving the catalytic nature of the presentinvention.

EXAMPLE 4

Methanol (212 mmol) was produced when a mixture containing ligand,2,2-bipyridine (5 mmol), in addition to reagents described in Example 2were heated at 100° C. and stirred in a reactor. The pressure drop ratewas 90, 28, and 12 psi/min for charges 1, 2, and 3 (300 psi each),respectively. Methanol alone accounted for 82% gas consumption.

EXAMPLE 5

The procedure in Example 2 was followed, except that the reactor waspressurized with syngas containing N₂ (instead of usual 2H₂ :1 COmixture), methanol was produced. The gas consumption rates were 46 and15 psi/min, respectively, for charges 1 and 2 (700 psi each containing400 psi N₂ and 300 psi 2H₂ :1 CO syngas), respectively. The N₂ gassimply passed through the system without affecting the catalyst. 639mmol methanol was produced accounting for >98% total gas consumption.

EXAMPLE 6

The procedure described in Example 2 was followed, except that the gasmixture contained between 84-90% CH₄, instead of normal 2H₂ :1 CO gasmixture. 153 mmol methanol was produced, accounting for >98% of thetotal gas consumed, showing that the methane did not affect catalystactivity.

EXAMPLE 7

The procedure described in Example 2 was followed except that theinitial gas mixture contained H₂ S. The rates were 33 and 5 psi/min forcharges 1 (300 psi containing 2% H₂ S) and 2 (300 psi containing 4% H₂S), respectively. 238 mmol methanol was produced, accounting for >99%total gas consumption, showing that the catalyst has high tolerance to Spoison.

EXAMPLE 8

A slight improvement in conversion rate was observed when K in place ofKH was used to prepare the alkoxide component. Thus, a solutioncontaining 40 mmol K-t-amyl alkoxide (prepared from potassium (40 mmol)and t-amyl alcohol (52 mmol)), 100 mL THF, 5 mmol Ni(CO)₄ was heated to100° C. under 300 psi syngas (2H₂ :1 CO) in the reactor. 260 mmolmethanol was produced. The rate was 26, 52, 25 psi/min for charges 1, 2,and 3 (300 psi each), respectively.

EXAMPLE 9

The following experiments were performed to establish the effect of theconcentration of the transition metal carbonyl component of the catalyston methanol synthesis rate. The procedure and set-up described inExample 8 was followed except that concentration of nickel tetracarbonylwas varied. Gas consumption rates are shown in Table 2 for charges 1, 2,and 3 (300 psi each).

                  TABLE 2                                                         ______________________________________                                                         Average Gas Consumption                                                                         Total                                      Ni(CO).sub.4                                                                          Charge   Rate              Methanol                                   mmol    No.      psi/min           mmol                                       ______________________________________                                         1      1         4                                                                   2        19                                                                   3        25                230                                        10      1        25                                                                   2        63                                                                   3        32                237                                        20      1        26                                                                   2        80                                                                   3        42                245                                        ______________________________________                                    

At a given base concentration (40 mmol in this case) the rate increaseswith increasing nickel carbonyl concentration but not in linear fashion.In every case, the process is truly catalytic.

EXAMPLE 10

This example illustrates that the catalyst activity for methanolsynthesis is not dependent on volume of solvent. K-t-amyl alkoxide (40mmol) was loaded into 300 mL, Parr reactor along with 20 mL THF. Afterpurging with H₂, the reactor was charged with 300 psi 2H₂ :1 CO gasmixture. The gas consumption rate was 36 psi/min. For charges 2 and 3(300 psi each), the rates were 47 and 30 psi/min, respectively,suggesting high volumetric efficiency with the present catalyst.

EXAMPLE 11

The rate of methanol synthesis is sensitive to base/nickel ratio. Thus,when one of the experiments in Example 9 was repeated withbase/nickel=100 mmol/1 mmol (100/1 ratio), the rates were 8, 40, 52psi/min for charges 1, 2, and 3 (300 psi each), respectively.

EXAMPLE 12

The procedures described in Example 8 were repeated withpotassium-t-amyl alkoxide replaced with 40 mmol K-t-butoxide (preparedfrom K and t-butyl alcohol). The rates were 12, 64, 30 psi/min forcharges 1, 2, and 3, respectively. The rate is dependent on the natureof alcohol from which the alkoxide is derived.

EXAMPLE 13

Repeating the experiment described in Example 8 with 40 mmol potassiummethoxide (KOMe) (this alkoxide is derived from MeOH, a primary alcoholas opposed to K-t-amyl alkoxide and K-t-butoxide which are derived fromtertiary alcohols), a significant improvement in rate was observed (74,31, 22 psi/min for charges 1, 2, and 3, respectively). 303 mmol MeOH wasproduced accounting for 97% syngas consumed.

EXAMPLE 14

0.1 mol of tetramethylammonium methoxide was dissolved in 100 mLmethanol diluted with 50% p-dioxane, and 5 mmol Ni(CO)₄ was added toprovide a completely homogeneous medium. The reactor was pressurized to800 psia with syngas (2H₂ :1CO) and heated to 120° C. The rate ofmethanol synthesis was 3 psi/min, comparable to that observed with KOCH₃under similar conditions.

EXAMPLE 15

The procedures described in Example 8 were repeated except that theco-solvent THF was replaced with the co-solvents shown in Table 3. Therate data are presented below in Table 3.

                  TABLE 3                                                         ______________________________________                                                        Rate (psi/min)                                                                  Charge   Charge   Charge                                    Solvent           1        2        3                                         ______________________________________                                        2-Methyltetrahydrofuran                                                                         22       17       4                                         1,2, Diethoxyethane                                                                             34       12       4                                         p-Dioxane         25       49       23                                        N-Methylmorpholine                                                                              40       12       3                                         t-Amyl alcohol     2        1       --                                        polyethylene glycol (PEG-400)                                                                   52       32       --                                        PEG400/Methanol (1:1 v/v)                                                                       92       --       --                                        ______________________________________                                    

The homogeneous catalyst performed most efficiently when THF, p-dioxaneor polyethylene glycol was used as the co-solvent.

EXAMPLE 16

200 mmol KOMe was dissolved in 100 mL of polyethylene glycol (PEG-400),and 10 mmol Ni(CO)₄ was added to give a completely homogeneous redsolution. The reactor was pressurized with 800 psia syngas (2H₂ :1CO)and heated to 120° C. The methanol synthesis initiated at below 50° C.and the rate was 52 and 32 psi/min for charges 1 and 2 respectively.

EXAMPLE 17

Methanol solvent was diluted with 50% PEG-400 and 400 mmol KOMe and 10mmol Ni(CO)₄ was added to form deep red catalyst solution. The initial820 psia syngas (2H₂ :1CO) pressure in the reactor decreased to 49 psiawith reaction initiating below 40° C. The methanol synthesis rate was 92psi/min and the highest temperature achieved during the reaction was115° C. intended temperature being 120° C. 296 mmol methanol wassynthesized with methanol selectivity >98.5%. The final solution was redand completely homogeneous and 94% CO conversion was achieved in lessthan 5 minutes.

EXAMPLE 18

40 mmol K-t-amyl alkoxide, 100 ml THF, and 5 mmol Ni(CO)₄ were mixedtogether under argon to give a red solution. After 2 days at roomtemperature, the red solution was loaded into the reactor and heated to100° C. after pressurizing to 300 psi with syngas (2H₂ :1 CO). Theactivity of the premixed catalyst was the same as that of fresh catalystsolution described in Example 8.

EXAMPLE 19

The effects of methanol build-up and base concentration on rates werestudied at 110° C. and 750 psi using 5 mmol nickel tetracarbonyl,p-dioxane as the co-solvent and KOMe as the alkoxide. The results asshown in Table 4.

                  TABLE 4                                                         ______________________________________                                        Solvent                                                                       p-Dioxane  Methanol                                                           mL         mL            Base   Rate                                          ______________________________________                                        100         0            100    180                                           90         10            100    102                                           75         25            100     15                                           50         50            100     3                                            75         25            400    224                                           ______________________________________                                    

Table 4 shows that rate decreases with increasing concentration ofmethanol at a given base concentration. But by simply increasing baseconcentration, the rate can be increased. This relationship betweenbase/MeOH ratio is described in the following example.

EXAMPLE 20

Solutions containing 5 mmol nickel carbonyl, 100 mL methanol andpotassium methoxide were heated at 110° C. under 750 psi (2H₂ :1 CO)syngas pressure. At higher base concentration (>400 mmol), the gas isconsumed even before desired temperature is reached. The followingresults of this experiment show that methanol synthesis rate isdependent on the KOMe/MeOH (base/solvent) ratio.

    ______________________________________                                               KOMe   Rate                                                                   (mmol) (psi/min)                                                       ______________________________________                                               400    11                                                                     600    >60                                                                    800    >>72                                                            ______________________________________                                    

EXAMPLE 21

Catalyst solutions containing 600 mmol KOMe, 100 mL MeOH, and Ni(CO)₄were heated at 110° C. under 750 psi (2H₂ :1CO) syngas pressure. Asshown in the following data, the rate increased with increasing nickelcarbonyl concentration.

    ______________________________________                                        Ni(CO).sub.4 Rate                                                             ______________________________________                                        1            15                                                               5            >60                                                              20           >>100                                                            ______________________________________                                    

At higher Ni(CO)₄ concentrations (e.g., 20 mmol), the gas is consumed in<3 minutes with concomitant formation of methanol.

EXAMPLE 22

The effect of reaction temperature on rate of methanol synthesis wasstudied. When 100 mL p-dioxane containing 100 mmol KOMe and 5 mmolNi(CO)₄ was pressurized to 750 psi with 2H₂ :1 CO syngas, the rate ofgas consumption was 15, 43, 63, 180 psi/1 min at 70°, 77°, 90°, 100° C.,respectively. An Arrhenius plot yielded E_(act) =23.3 Kcal/mole for thereaction. Methanol synthesis starts as low as room temperature at highercatalyst concentrations but the system operates well between 50°-150° C.

EXAMPLE 23

The present catalyst system can tolerate several traditional poisons,which adversely affect conventional methanol catalysts, as evidencedfrom rate data from batch reactions. Thus, with the catalyst system with400 mmol KOMe described in Example 20, the effect of various poisons wasas follows;

(1) with 750 psi syngas containing 8% CO₂ (rest is 2H₂ :1 CO), a 20%decrease in rate was observed;

(2) with 750 psi syngas containing 26% N₂, 7.4% CO₂, 2.5% H₂ S (rest was2H₂ :1 CO), the rate decreased by 50 %.

EXAMPLE 24

In one embodiment of the invention, 3.0 g dry Zeolite 13X (dried undervacuum at 400° C. for 4h) was added during reactor loading along with400 mmol KOMe in 100 mL methanol. The reactor was purged with H₂ and 5mmol Ni(CO)₄ was added. The reactor was pressurized with 750 psi (2H₂ :1CO) syngas and heated to 110° C. The rates were 10% higher compared withrates with catalyst solutions containing no Zeolite. The advantages ofusing a transition metal carbonyl support such as Zeolite include:

(1) virtual disappearance of methylformate, which is normally present insmall amounts as a by-product; and

(2) immobilization of Ni(CO)₄ onto the Zeolite. Gas phase infrared showsthat gas phase concentration of Ni(CO)₄ is decreased using the Zeolitesupport.

EXAMPLE 25

Twenty batch experiments were conducted to determine the effects oftemperature, methanol concentration, base concentration, P_(H2), P_(CO),and stirrer speed on reaction rate. Table 5 lists the conditions used ineach run. All runs were conducted using an initial Ni(CO)₄ concentrationof 0.05M except for Runs 1 and 2, which used an initial concentration of0.01M. Run 21 was conducted using methyl formate as a solvent withmethanol, while all other runs used either pure methanol or amethanol/p-dioxane mixture as the solvent.

The methanol, base, and Ni(CO)₄ liquid phase concentrations listed inTable 5 were calculated by assuming (1) no volume change on mixing ofp-dioxane, methanol, and KOCH₃ and (2) no density change of the liquidphase from 25° C. to reaction temperature. Therefore, the methanol,KOCH₃, and Ni(CO)₄ concentrations are more accurately described asmoles/liter at 25° C.

Runs 1 and 2 were the only runs conducted at an initial Ni(CO)₄concentration of 0.01M because the experiments were for a catalystconcentration that would give a reasonable rate of reaction. Areasonable rate of reaction was defined as one that would take betweentwo minutes and two hours to drop from the initial pressure of 750 psigto the final pressure of 100-150 psig. The rate of reaction in Runs 1and 2 was relatively slow and was expected to decrease further at thelower temperatures of interest. Therefore, for all subsequent runs, ahigher initial Ni(CO)₄ concentration of 0.05M was used. Thisconcentration of Ni(CO)₄ gave a reasonable rate of reaction.

Runs 3 and 5 were conducted to determine if mass transfer was limitingthe rate of reaction in the experiments. Runs 4, 7, 9, and 11 wereconducted at 116°, 70°, 98°, and 87° C., respectively, to determine theeffect of temperature on the rate of reaction. In Run 6 it was attemptedto repeat Run 4, but at a lower stirrer speed, to determine if masstransfer was limiting the rate of reaction. However, Run 6 was completebefore the reaction temperature reached that of Run 4.

Run 8 was the first run conducted with methanol present at the beginningof the reaction. This run was conducted at 90° C. because the rate ofreaction in a more concentrated methanol solution was not known. Therate at 90° C. was slower than anticipated, hence, for all subsequentruns in which methanol was present at the start of the reaction, thereaction temperature was maintained at about 110° C.

Runs 10, 12, and 13 were conducted to determine the effect of methanolon the reaction rate. The initial methanol concentrations used in theseruns were 25, 10, and 50 vol %, respectively. Runs 14, 15, and 16 werealso conducted to determine the effect of methanol concentration on thereaction rate at a different catalyst base loading. These runs wereconducted with initial methanol concentrations of 25, 75, and 100 vol %,respectively, and an initial KOCH₃ concentration of 4.0M.

Run 17, which was a repeat of Run 15 but at a higher stirrer speed, wasconducted to determine if mass transfer was limiting the rate ofreaction in the experiments with higher concentrations of base. Runs 18and 19, which were a repeat of Run 16 but at higher base concentrationswere conducted to determine the effect of base concentration on thereaction rate in a 100 vol % methanol solvent. Run 21, which was arepeat of Run 19 but with a 10 vol % methyl formate solvent, wasconducted to determine if methyl formate affected the rate of reaction.

In addition, one experiment (Run 18) was run to demonstrate that Ni(CO)₄and potassium methoxide were not consumed during the reaction andfunctioned as catalysts. This experiment was performed over a three-dayperiod by repeatedly pressurizing a vessel with syngas after thereaction had lowered the pressure to below 200 psig.

                  TABLE 5                                                         ______________________________________                                        Reaction Conditions for Batch Kinetic Experiments                                                                     Iso-                                                Initial  Initial          thermal                                             KOCH.sub.3                                                                             p-dioxane                                                                            Initial   Reaction                              Run   Stirrer Concen-  Concen-                                                                              Methanol  Temper-                               Num-  Speed   tration  tration                                                                              Concentration                                                                           ature                                 ber.sup.a                                                                           (RPM)   (M)      (Vol %)                                                                              (Vol %)                                                                              (M)  (°C.)                        ______________________________________                                         1.sup.b                                                                            1200    0.4      100    0      0    120                                  2.sup.b                                                                            1200    0.4      100    0      0    110                                  3     800    0.4      100    0      0    120                                  4    1200    1.0      100    0      0    116                                  5    1200    0.4      100    0      0    120                                  6     500    1.0      100    0      0    110                                  7    1200    1.0      100    0      0     70                                  8    1200    1.0       75    25     6.2   90                                  9    1200    1.0      100    0      0     98                                 10    1200    1.0       75    25     6.2  110                                 11    1200    1.0      100    0      0     87                                 12    1200    1.0       90    10     2.5  110                                 13    1200    1.0       50    50     12.4 109                                 14    1200    4.0       75    25     6.2  107                                 15    1200    4.0       25    75     18.5 110                                 16    1200    4.0       0     100    24.7 110                                 17    1800    4.0       25    75     18.5 109                                 18    1200    8.0       0     100    24.7 110                                 19    1200    6.0       0     100    24.7 109                                 20.sup.c                                                                            1200    6.0       0     90     22.2 110                                 ______________________________________                                         .sup.a Total solvent used = 100 ml for all runs.                              .sup.b [Ni(CO).sub.4 ].sub.0 = 0.01 M. For all other runs, [Ni(CO.sub.4)]     = 0.05 M.                                                                     .sup.c 10 vol % methyl formate was used in place of pdioxane.            

EXAMPLE 26

The following example demonstrates the synergistic effect of bimetallicsystems in methanol synthesis. 1 mmol Ni(CO)₄, 5 mmol copper methoxide,and 0.6 mol KOCH₃ were dissolved in 100 mL methanol. The reactor waspressurized with syngas (2H₂ :1CO) and heated to 120° C. Methanol wasproduced at a rate of about 5 psi/min.

EXAMPLE 27

5 mmol Ni(CO)₄ was added to a solution containing 0.4 mol KOMe dissolvedin 30% methanol/70% triethyleneglycol dimethylether (triglyme) mixtureand the reactor was pressurized to 750 psig syngas with H₂ /CO of 2/1ratio. The reactor when heated to 120° C. resulted in syngas consumptionrate of 115 psi/min.

We claim:
 1. A homogeneous catalyst for the production of methanol fromcarbon monoxide and hydrogen at low temperature and low pressure whichcomprises a transition metal material capable of generating thecorresponding transition metal carbonyl, wherein the transition metal isselected from the group consisting of Cu, Ni, Pd, Mo, Co, Ru, Fe, andmixtures thereof, and an alkoxide, dissolved in a solvent of methanolalone or methanol mixed with a co-solvent.
 2. The catalyst according toclaim 1 wherein the transition metal is selected from the groupconsisting of nickel, molybdenum, and copper.
 3. The catalyst of claim 1wherein the transition metal is nickel.
 4. The catalyst of claim 1wherein a co-solvent is used selected from the group consisting oftetrahydrofuran, p-dioxane, t-amyl alcohol, t-butyl alcohol, triglyme,and polyethylene glycols.
 5. The catalyst according to claim 1 whereinthe alkoxide component is derived from an aliphatic alcohol containingfrom 1-6 carbon atoms.
 6. The catalyst according to claim 1 wherein thetransition metal material generates nickel tetracarbonyl, the alkoxidecomponent is methoxide, and the catalyst is dissolved in a co-solvent ofmethanol and tetrahydrofuran.
 7. The catalyst according to claim 1wherein the transition metal material generates nickel tetracarbonyl,the alkoxide is methoxide, and the catalyst is dissolved in a co-solventsystem of methanol and p-dioxane.
 8. The catalyst according to claim 1wherein the transition metal material generates nickel tetracarbonyl,the alkoxide is methoxide, and the catalyst is dissolved in a co-solventsystem of methanol and polyethylene glycol or triglyme.
 9. A catalystfor the production of methanol from carbon monoxide and hydrogen at lowtemperatures and pressures in a methanol solvent system, which catalystis produced by the reaction of a transition metal carbonyl or atransition metal carbonyl precursor, or clusters of either, with a metalor amine compound that generates an alkoxide in the presence of themethanol solvent system.
 10. The catalyst of claim 9 wherein thetransition metal carbonyl reactant is nickel tetracarbonyl and thealkoxide generating reactant is an alkali or alkaline earth metalaliphatic alcoholate.
 11. The catalyst of claim 10 wherein the alkoxidegenerating reactant is potassium methoxide.
 12. The catalyst of claim 9wherein the alkoxide generating reagent is tetramethylammoniummethoxide.
 13. The catalyst of claim 9 wherein the alkoxide is generatedby a mixture of potassium methoxide and copper methoxide resulting in asupply of methoxide ions and in the formation of a nickeltetracarbonyl/copper carbonyl complex.
 14. The catalyst of claim 9wherein the methanol solvent system is comprised of methanol and aco-solvent.
 15. The catalyst of claim 9 wherein a support for thetransition metal carbonyl reactant is added.
 16. The catalyst of claim15 wherein the support is zeolite.